diff --git a/src/engine/evaluator.ts b/src/engine/evaluator.ts
index 67df2c4..238b3c1 100644
--- a/src/engine/evaluator.ts
+++ b/src/engine/evaluator.ts
@@ -1,6 +1,6 @@
 // Walks the AST with the document context (variables, line results for
 // sum/avg/prev) and produces unit-aware values.
-import { Decimal, EvalError, Quantity, Unit, Value, XRefError, qty, pct } from "./types";
+import { Decimal, EvalError, PI, Quantity, Unit, Value, XRefError, qty, pct } from "./types";
 import { Node, ConvTarget } from "./parser";
 import { Registry } from "./registry";
 import { resolveZone, startOfToday, addToDate, isCalendarUnit } from "./datetime";
@@ -28,7 +28,6 @@ export interface EvalCtx {
 export type XRefResolution = { ok: true; value: Value } | { ok: false; reason: string };
 export type XRefResolver = (sheet: string, key: string) => XRefResolution;
 
-const PI = new Decimal("3.14159265358979323846264338327950288419716939937510");
 const E = new Decimal("2.71828182845904523536028747135266249775724709369995");
 
 export function evaluate(node: Node, ctx: EvalCtx): Value {
diff --git a/src/engine/types.ts b/src/engine/types.ts
index d18b7c5..f009eba 100644
--- a/src/engine/types.ts
+++ b/src/engine/types.ts
@@ -4,6 +4,9 @@ Decimal.set({ precision: 40, toExpNeg: -9, toExpPos: 21 });
 
 export { Decimal };
 
+/** Shared here (not in evaluator.ts) so unitdata.ts can use it too without a cycle. */
+export const PI = new Decimal("3.14159265358979323846264338327950288419716939937510");
+
 export type Dimension =
   | "scalar"
   | "length"
diff --git a/src/engine/unitdata.ts b/src/engine/unitdata.ts
index 7b6692e..67548df 100644
--- a/src/engine/unitdata.ts
+++ b/src/engine/unitdata.ts
@@ -1,7 +1,7 @@
 // Conversion ratios. Base units per dimension: length=meter, area=m²,
 // volume=m³, weight=gram, time=second, angle=radian, data=bit,
 // temperature=kelvin (ratio+offset).
-import { Decimal, Dimension } from "./types";
+import { Decimal, Dimension, PI } from "./types";
 
 export interface UnitData {
   id: string;
@@ -79,7 +79,7 @@ export const UNIT_DATA: UnitData[] = [
 
   // Angle (base: radian)
   { id: "radian", category: "Angle", dimension: "angle", ratio: "1" },
-  { id: "degree", category: "Angle", dimension: "angle", ratio: String(Math.PI / 180) },
+  { id: "degree", category: "Angle", dimension: "angle", ratio: PI.div(180).toString() },
 
   // Data (base: bit)
   { id: "bit", category: "Data", dimension: "data", ratio: "1", prefixes: "data" },